[Heboil]

I know it has a closed light path, but I have some kind of dust blobs. I had a dust blob on the very bottom of my screen (only visible on very dark/black scenes), and I took the projector down and shot compressed air into the unit with the cover off. I then turned it on, and there were a few dust blobs all over the screen, albeit lighter than the one I had before. I have since taken the unit down half a dozen times and sprayed it out with compressed air. There are maybe two left now, and they are pretty faint, but I still see them at times. What is my best bet at getting rid of them (not including sending the projector in for service... I can't stand their service)? Thanks.